104 STEVENSON— FORMATION OF COAL BEDS. [April i8, 



immense areas have not so much ash as one should expect; they 

 have less than the original plants should have contributed. This is 

 the important matter for consideration ; there is no difficulty in 

 accounting for high ash in coal, but there is great difficulty in 

 accounting for coal which, in areas of thousands of square miles, 

 have too little ash. 



The ash in different beds as well as in different parts of the same 

 bed may show notable differences in composition. The White Ash 

 coal bed, of Upper Cretaceous age, near Cerillos in New Alexico, is 

 of interest because in the mines one can follow the coal in its passage 

 from high grade bituminous, thoroughly caking, with 39 per cent, of 

 volatile, and 5.24 of ash, to a typical anthracite with 93 per cent, of 

 fixed carbon and 5.78 of ash. This change takes place within little 

 more than 2,000 feet and is due to influence of a sheet of andesitic 

 rock. Church"^ analyzed the ash from both types, the samples being 

 taken from car-load lots and representing the coal as shipped to 

 market. His results are : 



Silica 26.93 32.14 



Alumina 3241 36.58 



Oxide of iron 3-96 12.86 



Lime 24.68 8.19 



Magnesia 10.32 5.11 



Sulphate of calcium 0.21 0.18 



Soda 1.36 



Potash 1.49 3-59 



McCreath^"" has given the composition of ash from 2 samples of 

 Red Ash and 7 of White Ash anthracite which may be compared 

 with that from the bituminous Upper Freeport at 3 localities in 

 Jefferson and Clinton counties. 



The bituminous coals contain 4.150, 3.100 and 9.125 per cent, of 

 ash respectively. A series of 21 analyses given by Muck^^'^ show 

 similar though greater variations. The silica is from 1.700 to 

 53.600; alumina from 2.210 to 41. no; sesquioxide of iron from 



"'W. D. Church, cited in J. J. Stevenson, "The Cerillos Coal Field," 

 Trans. N. V. Acad. Scl, Vol. XVL, 1896, pp. 117, 118. 

 "' A. S. AlcCreath, Rep. M, p. 27; Rep. MM, p. 375. 

 "" F. Muck, " Die Chemie der Steinkohle," pp. 98, 99. 



